On the decals, the new Echelon sets that are huge with all sorts of markings would be best. Remember though, the M1A1 and M2A2 will be from different Battalions, so their bumper #s and large unit ID numbers on the sides and back, and chevrons will be different, so you really don't need the decals all to be the same. The thing that needs to be the same is the Division, Battalions and Companies task organize (cross attach companies or platoons to mix tanks and Brads), Divisions don't usually mix units. If you have decals for a Tank Bn and a Mech (M2) Bn in 3 ID, you will be good. Certain Bns that are in the same BDE are the ones who always task organize, but only someone who is in the units would know if you have units from different BDEs mixed.
If you have the original Academy M1 kit, it is not a current M1A1 and a poor kit on top of it. For a full rundown of M1 Tank varients and their history, go here: http://www.msnusers.com/armorama/Documents/M1%20Abrams%20Tank%20Variants%2Edoc
Just hit cancel when it asks for a password and it will still come up.
For a good, current M1A1 model, go with either the New Tamiya M1A1/A2 kit, or for a cheaper option, the DML USMC Baghdad 2003 kit is correct for a Army M1A1 3ID. The Army parts are still in the kit and the new extended bussle rack is not a USMC version, but the US Army, 3ID version.
You are correct on the Bradley, USMC does not use them.
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